Simmons-Smith reaction Totally Explained

Everything about The Simmons-smith Reaction totally explained

The Simmons-Smith reaction is an organic reaction in which a carbenoid reacts with an alkene (or alkyne) to form a cyclopropane. It is named after Howard Ensign Simmons, Jr. and R. D. Smith.
   Thus, cyclohexene, diiodomethane, and a zinc-copper couple (as (iodomethyl)zinc iodide, ICH₂ZnI) yield bicyclo[4.1.0]heptane.
   Alternatively, diethylzinc is used instead of the zinc-copper couple.
   The Simmons-Smith reaction is generally subject to steric effects, and thus cyclopropanation usually takes place on the less hindered face. However, when hydroxy substituents are present on chiral carbons, the zinc coordinates with the hydroxy substituents, directing cyclopropanation to the same face, which may or may not be sterically favorable :
The Simmons-Smith reagent, namely diiodomethane and diethylzinc, can react with allylic thioethers to generate sulfur ylides, which can subsequently undergo a 2,3-sigmatropic rearrangement, and won't cyclopropanate an alkene in the same molecule unless excess Simmons-Smith reagent is used:

Asymmetric Simmons-Smith reaction

Although asymmetric cyclopropanation methods based on diazo compounds (see bisoxazoline ligand) exist since 1966, the asymmetric Simmons-Smith reaction was introduced in 1992 with a reaction of cinnamyl alcohol with diethylzinc, diiodomethane and a chiral disulfonamide in dichloromethane:
The hydroxyl group is a prerequisite serving as an anchor for zinc. In another version of this reaction the ligand is based on salen and Lewis acid DIBAL is added :

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